﻿/*-
 * Copyright 2003-2005 Colin Percival
 * Copyright 2012 Matthew Endsley
 * All rights reserved
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted providing that the following conditions 
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <limits.h>
#include "bspatch.h"

static int64_t offtin(uint8_t *buf) {
    int64_t y;

    y = buf[7] & 0x7F;
    y = y * 256;
    y += buf[6];
    y = y * 256;
    y += buf[5];
    y = y * 256;
    y += buf[4];
    y = y * 256;
    y += buf[3];
    y = y * 256;
    y += buf[2];
    y = y * 256;
    y += buf[1];
    y = y * 256;
    y += buf[0];

    if (buf[7] & 0x80) y = -y;

    return y;
}

int bspatch(const uint8_t *old, int64_t oldsize, uint8_t *news, int64_t newsize,
            struct bspatch_stream *stream) {
    uint8_t buf[8];
    int64_t oldpos, newpos;
    int64_t ctrl[3];
    int64_t i;

    oldpos = 0;
    newpos = 0;
    while (newpos < newsize) {
        /* Read control data */
        for (i = 0; i <= 2; i++) {
            if (stream->read(stream, buf, 8))
                return -1;
            ctrl[i] = offtin(buf);
        };

        /* Sanity-check */
        if (ctrl[0] < 0 || ctrl[0] > INT_MAX ||
            ctrl[1] < 0 || ctrl[1] > INT_MAX ||
            newpos + ctrl[0] > newsize)
            return -1;

        /* Read diff string */
        if (stream->read(stream, news + newpos, ctrl[0]))
            return -1;

        /* Add old data to diff string */
        for (i = 0; i < ctrl[0]; i++)
            if ((oldpos + i >= 0) && (oldpos + i < oldsize))
                news[newpos + i] += old[oldpos + i];

        /* Adjust pointers */
        newpos += ctrl[0];
        oldpos += ctrl[0];

        /* Sanity-check */
        if (newpos + ctrl[1] > newsize)
            return -1;

        /* Read extra string */
        if (stream->read(stream, news + newpos, ctrl[1]))
            return -1;

        /* Adjust pointers */
        newpos += ctrl[1];
        oldpos += ctrl[2];
    };

    return 0;
}

#if defined(BSPATCH_EXECUTABLE)

#include <bzlib.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <err.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>

static int bz2_read(const struct bspatch_stream* stream, void* buffer, int length)
{
    int n;
    int bz2err;
    BZFILE* bz2;

    bz2 = (BZFILE*)stream->opaque;
    n = BZ2_bzRead(&bz2err, bz2, buffer, length);
    if (n != length)
        return -1;

    return 0;
}

int main(int argc,char * argv[])
{
    FILE * f;
    int fd;
    int bz2err;
    uint8_t header[24];
    uint8_t *old, *news;
    int64_t oldsize, newsize;
    BZFILE* bz2;
    struct bspatch_stream stream;
    struct stat sb;

    if(argc!=4) errx(1,"usage: %s oldfile newfile patchfile\n",argv[0]);

    /* Open patch file */
    if ((f = fopen(argv[3], "r")) == NULL)
        err(1, "fopen(%s)", argv[3]);

    /* Read header */
    if (fread(header, 1, 24, f) != 24) {
        if (feof(f))
            errx(1, "Corrupt patch\n");
        err(1, "fread(%s)", argv[3]);
    }

    /* Check for appropriate magic */
    if (memcmp(header, "ENDSLEY/BSDIFF43", 16) != 0)
        errx(1, "Corrupt patch\n");

    /* Read lengths from header */
    newsize=offtin(header+16);
    if(newsize<0)
        errx(1,"Corrupt patch\n");

    /* Close patch file and re-open it via libbzip2 at the right places */
    if(((fd=open(argv[1],O_RDONLY,0))<0) ||
        ((oldsize=lseek(fd,0,SEEK_END))==-1) ||
        ((old=malloc(oldsize+1))==NULL) ||
        (lseek(fd,0,SEEK_SET)!=0) ||
        (read(fd,old,oldsize)!=oldsize) ||
        (fstat(fd, &sb)) ||
        (close(fd)==-1)) err(1,"%s",argv[1]);
    if((news=malloc(newsize+1))==NULL) err(1,NULL);

    if (NULL == (bz2 = BZ2_bzReadOpen(&bz2err, f, 0, 0, NULL, 0)))
        errx(1, "BZ2_bzReadOpen, bz2err=%d", bz2err);

    stream.read = bz2_read;
    stream.opaque = bz2;
    if (bspatch(old, oldsize, news, newsize, &stream))
        errx(1, "bspatch");

    /* Clean up the bzip2 reads */
    BZ2_bzReadClose(&bz2err, bz2);
    fclose(f);

    /* Write the news file */
    if(((fd=open(argv[2],O_CREAT|O_TRUNC|O_WRONLY,sb.st_mode))<0) ||
        (write(fd,news,newsize)!=newsize) || (close(fd)==-1))
        err(1,"%s",argv[2]);

    free(news);
    free(old);

    return 0;
}

#endif
